


Baptism by Fire

by impertinentfool



Category: Avatar: The Last Airbender, 鬼滅の刃 | Demon Slayer: Kimetsu no Yaiba (Anime), 鬼滅の刃 | Kimetsu no Yaiba (Manga)
Genre: Alternate Universe - Canon Divergence, Cross-Posted on FanFiction.Net, Crossover, Drama, Fluff and Humor, Gen, Kyojuro and Zuko as accidental siblings, Senjuro will be involved here one way or another, Slight Canon Divergence, Spirits have something to do with this, a roundabout way of doing therapy, demon slayer is no exception, field trips with zuko transcends worlds, fire lord zuko hijacks senjuro's body, friendships and perpetual confusion abound, kyojuro and zuko try to outbrother each other, poor senjuro, the chaos that follows isn't entirely his fault, ty lee and kanroji should meet
Language: English
Status: In-Progress
Published: 2020-05-19
Updated: 2020-05-19
Packaged: 2021-03-03 05:40:39
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,252
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24249700
Author URL: https://archiveofourown.org/users/impertinentfool/pseuds/impertinentfool
Summary: “We were blessed,” his father spits out, alcohol clearly muddling his brain. “By the gods. Your brother—I saw him. The fire. I saw him. You wouldn't understand.” There’s an odd mixture of pride and bitterness in that statement.Father’s right, Kyoujurou admits. He does not.—Rengoku Senjurou prayed for the god of fire. What he got instead was a disgruntled firelord.
Comments: 17
Kudos: 117





	Baptism by Fire

**Author's Note:**

> this was inspired by this [tumblr post](https://www.reddit.com/r/tumblr/comments/fmda0j/hello_zuko_here/)
> 
> Wrote this also because I wanted to write about Zuko and Kyojuro meeting each other, and this happened. This is the prologue, a strange interlude of sorts, and the characters' circumstances will be further expounded in the later chapters, if this doesn't remain as a oneshot. Zuko in this story alternates between awkward dork and self-assured king, it's great. And as always, Kyoujurou is best boy. 
> 
> (*whispers* i'm doing a kyoujurou/azula + zuko fic and i hope to post it sooner or later on october!! hell yeaaa) 
> 
> an idea of senjuko's sword, minus the red blade: [katana](https://medievalswordsworld.com/wp-content/uploads/2019/07/KatanaWithSaya.jpg)
> 
> [tumblr!](https://rengokuestate.tumblr.com/) | [twitter](https://twitter.com/rengokuestate) ; @rengokuestate--feedback is appreciated (but i mostly just rt stuff)

Senjurou's sword turns red the moment his hand touches the hilt.

The elderly swordsmith makes a pleased murmur behind his mask, and Kyoujurou barely refrains from pulling his brother into a soul-crushing hug.

"Congratulations, little brother!"

Senjurou doesn't respond, still gazing at the sword. Kyoujurou doesn't blame him – its hilt a combination of black and red, handguard shaped into a smooth ring of intricate bronze. The sheen of its red blade glares at them, and it looks powerful and intimidating. A bit more minimalistic compared to Kyoujurou's, but the simplicity adds to its elegance.

 _Destroy all demons,_ emblazoned near the hilt.

"What a beautiful sword! Fitting for a Rengoku!"

Senjurou still remains silent, at a loss for words, and Kyoujurou understands. He could still remember the chest-bursting happiness he felt when color materialized in his own sword. Nichirin Blades are a demon slayer's lifeline, a solid reminder of their purpose.

"It's shiny," says Senjurou. And then backtracks for a second. "I mean, it's a gorgeous sword. Thank you."

Swordsmith-san nods in affirmation.

"Indeed, indeed!" Kyoujurou sings praises beside him.

His little brother blinks like an owl. "Uh, and it's sharp. Really sharp."

"Yes! Commit oneself to eradicating Kibutsuji Muzan and his followers!"

A cough. "Sure."

The swordsmith makes a noncommittal sound beneath his mask.

"I'm sure I can kill demons with this," says Senjurou. He glances at Kyoujurou as his voice tries to sound louder and firmer at that last part. Kyoujurou's lips tug at a grin as he observes Senjurou. That undeterred enthusiasm, rising up to match his older brother. Commendable!

"Yes, of course. It can cut, too," the swordsmith deadpans.

A beat.

"What are you-"

"Ah, as expected! Such fine craftsmanship!" Kyoujurou laughs and interjects before Senjurou tries his new sword on the elderly. "We are in your debt, as always."

The swordsmith mutters a quiet "you're welcome" in response, and Senjurou crosses his arms, grumbling under his breath.

Still, he bows in gratitude one last time as the swordsmith prepares to leave the estate. Sounds of footsteps descending, and then silence for a while.

The sky is nearly dark, sun just beginning to rise in the horizon. The overcast morning sky looms in the dawn.

It is shaping up to be a wonderful day, morning dew present from yesterday's rain. They sit together on the engawa overlooking the garden. A low table sits between them, bearing two porcelain cups and a teapot. In the cold air, birds titter around. Peaceful. Serene.

"I don't understand why that man had to snark at me," Senjurou breaks the silence, sullen voice and frown in place. "And after we just praised him till kingdom come."

"Some people are just like that!" says Kyoujurou, trying to reassure him. "Don't let it bother you too much."

Senjurou frowns.

"You're going to be my tsuguko!" Kyoujurou shouts joyfully, trying to lighten up the mood. "I am so proud of you! And so young, too! Younger than I was. Father will be joyous!"

_His father's back faced towards him, as he laid in his futon, pointedly disregarding his son. Stating that everything was meaningless-_

Kyoujurou banished it from his mind.

"Thank you," says Senjurou, smiling at him. "Your praise means a lot, Onii-sama."

"Of course! And call me Anuie! Or even Aniki! No need to be so formal all the time, we're brothers!"

"No, I'll still call you Onii-sama," says Senjurou. Defiant, sitting next to him with that excellent posture and smirk. Back straight and stiff, like a Lord in all his thirteen years of glory. Staring at him with those unusual amber eyes. Kyoujurou can't help but feel like he's secretly being made fun of.

"That's fine as well. Respectful!"

"You know, all that training really paid off. It was a literal pain at times, but you're a great teacher. I can see why Kanroji adores you so," Senjurou remarks.

"Such kind words! And that's not fair."

"What is?"

"You refer to Kanroji so informally!"

"Don't tell me you're jealous?" Senjurou smirks, eyes crinkling up. Kyoujurou bristles inside, feeling self-conscious all of a sudden.

"I am not!"

"Yes. Clearly you're not."

There he is again! No, Kyoujurou's not pouting! A Rengoku would never reveal their weakness so openly. Kyoujurou wants to reach out and ruffle Senjurou's hair, see if he likes that!

"Well, she reminds me of an old friend. I like her," Senjurou tells him matter-of-factly as he pours out a cup for himself. And he does. Always bringing her tea and making small talk in the year when she stayed inside the Rengoku residence to train as Kyoujurou's chosen tsuguko. Giving her small treats when he thinks Kyoujurou isn't looking in their direction. "Not in that way, of course. I just like her."

_An old friend?_

Kyoujurou's mildly astonished that there was something he didn't know yet about his baby brother. Before he can inquire further, however, Senjurou hands him the cup. "Here. Drink it before it gets cold."

"Ah, thank you!" He takes the cup and is surprised for a second. It scalds his fingers with its heat. Still, not wanting to displease his brother, he takes a quick sip. It nearly burns his tongue, but the flavor is there.

"Delicious!" he exclaims, louder than before. He takes a slower, deliberate sip. It's mild, not too strong, but it leaves a subtly sweet impression on his mouth. The smell is fragrant as well. Soothing, as tea should be.

The nostalgia settles in his bones, a wistfulness tempered by days long forgotten and embraced. They would sit like this, too, with Kyoujurou resting his head on their mother's lap, the sense of fingers on his scalp and traces of Ruka's warmth, a scent of bamboo oils, lethargic and all things wonderful.

There was always a cup for her, too, for the body. Ginseng was Mother's favorite. To cure the weariness apart from the illness that was incurable. He could still remember.

Some days they'd watch their father practice with his blade, until the time that Kyoujurou was there himself. Senjurou was still too young so he'd watch them instead with a certain fondness. Those were the good old days.

"Delicious!" Kyoujurou repeats. "You've gotten better at brewing tea!"

It's this statement, of all things, that actually brightens every corner of Senjurou's face. "Really? I'm glad you like it. I learned from the best."

"Someone tutored you? I thought you said that you read Mother's books on how to make tea?"

"That's not really important," Senjurou waves him off. "I won't reveal my tea secrets, so don't ask any more questions."

"Okay!" Oh well. Senjurou was so forceful sometimes.

"Can you guess what kind of tea it is?"

"I'll try!" Another sip. Flowery, wonderful. "I see. It's jasmine! You're really fond of it, aren't you?"

"It's tea. What's not to love?"

"You should open up a tea shop!"

"Oh yes, a Rengoku family teashop. You can be head waiter, charming and distracting folks, while I brew tea in the corner. Let's see what _Father_ has to say about that."

Kyoujurou holds his laughter. "He'd blow a gasket!"

"Good. Someone has to entertain the customers, and he'd be perfect for the job."

On any other day, Kyoujurou would have chastised him about showing disrespect towards their father, but the absurdity of it all gets to him. Kyoujurou guffaws out loud and holds his stomach. The mental image!

"It's not that funny," says Senjurou, but his own eyes were laughing and twinkling.

"Imagine if my fellow Hashira became our customers!"

"Tomioka's nice."

"Nice?" _Tomioka Giyuu?_ "He's certainly genial when he wants to be. A man of few words, that Tomioka. He's a good comrade."

Senjurou hums while he pours a cup. "I can respect that."

"You two would get along well! Give him joint ownership!"

"You're really getting into it. Mother would probably be rolling in her grave right now," says Senjurou. And then his smile disappears as quickly as it appeared. "Sorry about that."

He knows how much Kyoujurou holds her in high esteem.

"It's fine!" Kyoujurou exclaims, patting Senjurou on the shoulder. It doesn't bother him, but it does sober him up.

"But what if I'm serious?" says Senjurou, regarding him with a careful stare. Kyoujurou decides to humor him.

"About living your dream as a teashop owner?"

"What if I choose to do something else other than being a demon slayer?"

"Oh."

Kyoujurou can't tell if he's joking.

"Well?"

He's serious.

It takes a while for Kyoujurou to answer, but when he does, it's honest and true. "In that case, go for it! Whatever endeavor you wish to partake in, your big brother is here to support you!" The words sound right, and Kyoujurou is surprised to feel that he means it, even when he feels a little disappointed in Senjurou, when he showed so much untapped potential.

He should've noticed the signs, Kyoujurou thinks. Senjurou always showed a hint of disinterest whenever they were discussing demons. He seemed focused, but not as passionate as Kyoujurou was when he was the same age. Almost as though Senjurou was distracted. Even when Father still trained them when they were young, and the weight of the world didn't crash down on the former Flame Hashira.

Senjurou sighs, putting the table aside and shuffling closer to Kyoujurou, who regales him with a curious stare. Senjurou stares, and then something flits in his eyes, as though he has seen something in his brother's face.

"Kyoujurou."

It's strange, the way his name rolls off Senjurou's tongue, like a declaration.

"Follow your heart! Set it ablaze! If you are truly serious in your dream, then nothing else matters-!"

The swordsmith wasted his time and his strength. Senjurou's Nichirin Blade would gather dust if he didn't take the pledge, and it would only serve as an ornament in the house, a future family heirloom, but _that was fine!_

"-you have other talents in other areas! And that's _wonderful_! Your passion shouldn't be centered around demon slaying!"

What would Father think? The thought leaves a sinking feeling in his gut.

But if Shinjuro Rengoku refused the call years ago, then he shouldn't have qualms about his youngest son not following the family tradition! Kyoujurou will never let anyone, not even their own father, hinder Senjurou's path!

Still. _Father would've been proud_. Nowadays, he was always more expectant and lenient towards Senjurou. An odd juxtaposition that Kyoujurou never truly understood.

"Kyoujurou." Senjurou repeats. There's a strange expression on his face, a smile beginning to form. Eyes staring at him with warmth.

"Listen to me. You are the best brother anyone can ask for. Your honor burns like the sun."

"That's-" Kyoujurou starts to say, but his chest flares with an unusual fury. "Thank you!" he chokes out instead.

"Fine then. I've decided. I'll become your tsuguko. I'll train even harder and I won't soil the family name." Senjurou declares, raising his chin high. An ultimatum. A decision.

His ears slowly turn red.

Cute! Kyoujurou can't help but chant in his head. A bashful Senjurou is always amusing to see!

"But most of all, I'll do it for you."

This time, Kyoujurou tackles him into a hug. Senjurou feels small like this, and he's reminded of the times they'd sleep beside each other, when they were still very little. "Yes! Let's become strong together and defeat all the demons!"

His little brother struggles in his grip, half-heartedly batting him away. "You're squeezing me!"

Kyoujurou laughs.

"Your tea! It's getting cold!"

"Is tea more important than your brother expressing his happiness?"

"Yes!"

Eventually, he relents, and lets go. Senjurou folds his arms, staring at him in mock disapproval.

"What?" Kyoujurou can't help but feel amused.

"Your tea."

Still with the tea? Kyoujurou reaches out for it, but Senjurou takes it before he can. "I'll just refill your cup first." Senjurou does, and then for a while he holds the cup with both palms. "Here."

"I'm going to be your first regular when you finally set up that teashop," Kyoujurou teases him, and accepts the offered tea. When he sips, it feels warmer for no apparent reason. 

"Hot!"

"Oh, sorry for that."

"Why are you apologizing? It's not your fault!" Kyoujurou laughs.

"Nothing." Senjurou looks up at the white, pale skies. "It's going to be really sunny today. Let's enjoy the morning chill while it lasts."

There's no sign of any sun peeking from the clouds. Kyoujurou shakes his head. "On the contrary, a rain shower seems to be approaching once again."

"Trust me, the sun will be insistent. It feels different."

It's entertaining, when Senjurou talks like this, but Kyoujurou's not going to argue with him about the weather, of all things.

"I didn't know you can communicate with the sun!" Kyoujurou quips, amusement leaking through his tone. Not quite mocking. Not quite serious, either.

This time, Senjurou chortles, sudden and joyful and rare, followed by Kyoujurou's resounding laughter.

"Now you know."

Seconds become minutes, and minutes become an hour. They finish the tea together, and then it starts to rain. As he predicted. Childish it may be, Kyoujurou feels a smug sense of vindication.

"A rain shower," Senjurou concedes before he picks up the tray and leaves.

The rain comes, and quickly goes, fleeting as a shroud in the wind. But then the sun does come, waves of immense heat scouring over the land, letting the white cotton of his _nagajuban_ stick to his skin.

Kyoujurou stands, and soon he prepares for the day.


End file.
